The present invention relates to a polyester resin composition which is excellent in any of plasticity, compatibility, retention and resistance to volatilization.
Polyester resins, typically polyethylene terephthalate, polybutylene terephthalate and the like, are widely used for manufacturing molded articles, synthetic fibers, etc. because of their superior properties. However, when used in preparing sheets, films, hoses and so on, a polyester resin should be plasticized by adding a modifier having a high compatibility with the polyester resin and a high plasticity.
Examples of such modifiers are aromatic ester compounds, aromatic ether compounds, alkyldiphenyl compounds, aromatic imide compounds, etc. Yet, these compounds are unsatisfactory in properties. For example, aromatic ester compounds, although relatively good in compatibility with polyester resins, have a problem of reducing the polymerization degree of the resin when melted together with the resin, resulting in impaired mechanical properties. Aromatic ether compounds, alkyldiphenyl compounds and aromatic imide compounds have problems that they are difficult to add in an amount sufficient to plasticize the resin owing to their low compatibility with the resin and that they are likely to bleed from molded articles due to the poor retention of the modifier in the resin. In short, polyester resin compositions with fully satisfactory properties are unknown at present.